With improved and more cost-efficient manufacturing techniques, flat panel displays such as liquid crystal displays (LCDs), organic light-emitting displays (OLEDs) and plasma display panels (PDPs) are now widely available to consumers. An LCD can be generally classified into three types, namely, reflection LCD, transmissive LCD, and transflective LCD. A transmissive or a transflective LCD generally includes an LCD panel and a backlight module. The LCD panel has a liquid crystal layer sandwiched between two transparent substrates. The backlight module provides a light source to illuminate the LCD panel for displaying images.
FIG. 1 is a cross-sectional view showing a conventional direct-type backlight module. The conventional direct-type backlight module 100 includes a light emitting diode (LED) array substrate 120 and a diffusion plate 190. The LED array substrate 120 has a plurality (an array) of LEDs 122, which can emit red light, green light, and blue light. The red light, green light, and blue light are mixed to form white light over the LED array substrate 120. The diffusion plate 190 is disposed over the LED array substrate 120 for diffusing the light.
Because the divergence angles θ of the light emitted from the conventional LEDs 122 are relatively small, a distance D1 is maintained between the diffusion plate 190 and the LED array substrate 120 to allow sufficient mixing of light of various colors emitted by the LEDs 122 such that uniform white light can be provided by the direct-type backlight module 100. The required distance D1 between the LED array substrate and the diffusion plate prevents reduction of the thickness of conventional direct-type backlight modules, which may limit the ability to achieve very slim LCD devices.